1. Field of the Invention
The present invention relates to an IPv6 compatible router for forming a network of IPv6, which is a new basic protocol for the Internet.
2. Description of the Related Art
The Internet is a network interconnected worldwide, and has been spreading rapidly. IPv6 is a technology for drastically solving the shortage of addresses on the Internet that has thus spread explosively, and IPv6 is expected to be spread widely. There are two kinds of IPv6 addresses: aggregatable unicast global addresses and site-local addresses. Aggregatable unicast global addresses are used in connecting to the Internet, whereas site-local addresses can be used freely within a site.
FIG. 8 is a diagram showing a format of an aggregatable unicast global address. As shown in FIG. 8, an IPv6 address comprises a 64-bit position identifier (prefix) and a 64-bit interface identifier (interface ID). The position identifier comprises a 3-bit format prefix (FP), a 13-bit top-level aggregation identifier (TLA ID), an 8-bit reserved field for future use (RES), a 24-bit next-level aggregation identifier (NLA ID), and a 16-bit site-level aggregation identifier (SLA ID). The interface ID is used to uniquely identify an interface on a link. The interface ID is required to be unique on the link. The interface ID generally uses a 32-bit MAC address of the host in a part of the field.
FIG. 9 is a diagram showing a format of a site-local address. The site-local address comprises a position identifier portion (prefix) composed of the most significant 48 bits set fixedly and a 16-bit subnet ID, and a 64-bit interface identifier portion (interface ID). The most significant 48 bits of an aggregatable unicast global address is assigned from a connected ISP or the like. A company or a household connected to the Internet uses the SLA field to construct a network within the company or the household. Conventional networks using IPv6 require distribution of unique IP addresses. Initial IPv4 networks for example required the trouble of manually determining IP addresses for host units and setting the IP addresses in the individual hosts. Thereafter DHCP (Dynamic Host Configuration Protocol) was developed as a protocol for assigning addresses to hosts, thus making it possible to construct an environment usable without manual setting of hosts.
DHCP is defined in RFC 2131, “Dynamic Host Configuration Protocol.” Such a so-called Plug & Play technique, which eliminates setting by a user, is important for enabling a user unaccustomed to setting and the like to use an IP net easily, for example. IPv6 allows automatic generation of an IP address for a host according to a neighbor discovery protocol without a DHCP server, thus greatly improving usability thereof. According to the neighbor discovery protocol, a router advertises an IP address position identifier of the link to a host, and the host generates an IP address on the basis of the position identifier.
The IP address is defined in RFC 2373, “IP Version 6 Addressing Architecture,” and RFC 2374, “An IPv6 Aggregatable Global Unicast Address Format.” The neighbor discovery protocol is defined in RFC 2461, “Neighbor Discovery for IP Version 6 (IPv6).” The automatic address generation by the host is defined in RFC 2462, “IPv6 Stateless Address Autoconfiguration.”
On the other hand, the router, which is another entity for forming an IP network, needs to be assigned a unique address. It is therefore necessary to design the address manually, as is conventional, and set the value in the router.
FIG. 10 is a diagram representing a method of automatically generating an address by a host. A 64-bit prefix of an IPv6 address is manually set to a port 4 of an IPv6 router 2. The most significant 48 bits of the prefix is assigned from an ISP or the like, and the SLA of the least significant 16 bits is designed by a network constructor such as an operator or the like. As indicated by (2), the IPv6 router 2 periodically advertises the 64-bit prefix of a network connected to the port 4 in a Router Advertisement message from the port 4 according to the neighbor discovery protocol.
Hosts 6#1 and 6#2 receive the Router Advertisement message, and thereby obtain the 64-bit prefix. As indicated by (4), the hosts 6#1 and 6#2 obtain a 64-bit interface identifier portion on the basis of a MAC address set in LAN cards 8#1 and 8#2. Then, the hosts 6#1 and 6#2 combine the prefix with the interface identifier portion, and thereby obtain a 128-bit IP address.
Thus, a company or a household connected to the Internet uses the SLA field to construct a network within the company or the household. Hence, although an assigned value may be used as it is as the most significant 48 bits, the SLA value needs to be assigned to each router such that the SLA value is unique in the internal network. A site-local address has the most significant 48 bits thereof set fixedly. The address in this format also requires a subnet ID field to be used and assigned to each router so as to be unique in the internal network.
However, conventional address design and assignment in a company or the like is currently performed by an organization that manages the network, and this work requires knowledge of IPv6. Therefore IPv6 networks are not introduced smoothly into households, companies and the like where a person with such knowledge is not very likely to be present.